Siphula ceratites

C24H26O7, Mr 426.47, cryst., double mp. 185°C (decomp.) and 228-229 °C. A chromone from the shrublike lichen Siphula ceratites. A rare example of a polyketide with more than 20 C atoms, probably formed by condensation of an octanoyl starter with 8 malonate units. 

Gaskell SJ, Eglinton G, Bruun T (1973) Hydrocarbon constituents of three species of Norwegian lichens Cetraria nivalis, C. crispa, and Siphula ceratites. Phytochemistry 12 1174-1176... 

Shimada S, Saitoh T, Namiki Y, Sankawa U, Shibata S (1980a) New siphulin derivatives from the lichen Siphula ceratites. Phytochemistry 19 467-469 Shimada S, Saitoh T, Sankawa U, Shibata S (1980b) New depsidones from Lobaria oregana. Phytochemistry 19 328-330... 

Obtained by alkaline degradation of various siphuUn derivatives with potassium hydroxide in refluxing methanol [3657], The siphulin (an homoflavone) 7-hydroxy-5-heptyl-2-[3, 5 -dihydroxy-2-carboxybenzyl]chroman-4-one (m.p. 180°) [3658] is a constituent of the North Scandinavican lichen siphula ceratites (Wahlenberg) Fr. 

The plant growth hormone ethylene was detected in the lichen Ramalina duriaei by Epstein 281, 282). Ott and Zwoch 569) analyzed Cetraria islandica, Cladonia rangiferina, C. arbuscula, C. sulfurina, C. cornuta, C. pyxidata, Peltigera lactucifolia and Usnea aurantiaco-ater for ethylene and found it in amounts of 0.8-5.5 pl/g dry weight/ hour. The presence of hydrocarbons with 17-33 carbon atoms has been reported 317) in Cetraria nivalis, C. crispa and Siphula ceratites in other lichens C-27, C-29 and C-31 were the main hydrocarbons 765). The hydrocarbons of the odoriferous fraction of Evernia prunastri have been examined 357). 

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